In order to satisfy a demand for the higher performance of an electronic apparatus, besides scaling-down and multiple functions of each device chip itself, as an influential means, the improvement in additional values may be exemplified which is introduced by complexing applications based on the integration of a plurality of chips having various functions. For example, in a case where a wireless communication apparatus is added with a new application, as a valid aspect, it may be considered that analog processing circuits for wireless communication and digital circuits for signal processing are consolidated into one chip. For the realization of the above aspect, various requirements for design specifications exists, in particular, requirements for a technology of constructing a package of the device chip and, requirements for a technology of mounting the chips.
Specifically, in a case of mounting a high-frequency semiconductor chip or a power semiconductor chip, since the strength of signals passing through the chip is great (several Watts or more) or the frequencies of the signals are high (several GHz or more), and electrical impedance matching or a reduction in insertion loss are necessary, a large number of requirements for the mounting technology are present. For this reason, there have been many problems in design and processes for making a package and then a module.
In the related art, as an example of a widely-used configuration, each of the semiconductor chips is sealed in a package material made of metal, ceramic, or a complex of these and then the chips are configured to be mounted on a printed circuit board and the like as a module together with other elements such as passive components. For example, a high-frequency chip called an MMIC (Monolithic Micro wave Integrated Circuit) is needed to combine the electrical impedance matching between input and output units with the reduction in insertion loss of electric signals. In order to satisfy the need, a package material including metal, ceramic, or a complex of these is subjected to die bonding with a material such as Au and Au (Sn), subjected to wire bonding with Au wires and the like, and hermetically sealed, thereby being completely formed as one package. The packages formed in this way are mounted on a printed circuit board through soldering, wire bonding, and the like together with capacitors, inductors, resistors, and the like, and thus the high-frequency modules are completed as a system.
However, since the ranges of usable frequencies are wide by several digits and even the types of transferable power vary depending on the high-frequency semiconductor chips, it is necessary to select the package and the mounting method which are suitable to the corresponding usage environment. Further, in a case where a plurality of the semiconductor chips having different functions are formed in a package or a module, regarding the scaling down and high integration of the package itself, there is a request for constructing a new mounting technology in which the package can be configured without using a large-scaled ceramic package or the like.
In addition, in a case of the power semiconductor chip, since a large amount of heat generation is accompanied, there is a request for a material and a package structure excellent in thermal conductivity for wasting the generated heat. For this reason, there is a strong demand for the development of a mounting technology in order to realize the power semiconductor chip using a small-size and low cost package.